An increasing number of surgical techniques are now performed arthroscopically. One type of arthroscopic procedure reconstructs the anterior cruciate ligament (ACL) in the knee. Several ACL reconstruction techniques are described in U.S. Pat. No. 5,139,520 (issued Aug. 18, 1992, known herein as “the '520 patent”) and incorporated by reference.
A substitute graft harvested from the patient or from a donor usually replaces an ACL that has ruptured and is non-repairable. The substitute ACL graft may be a portion of a patellar tendon having so called “bone blocks” at each end. A method and an apparatus for harvesting such a patellar tendon graft is described in U.S. Pat. No. 5,733,289 (issued Mar. 31, 1998, known herein as “the '289 patent”) and incorporated by reference. Alternatively, an artificial graft formed from synthetic materials or from a combination of artificial and natural materials may be used and is sometimes referred to as a ligament augmentation device (LAD). The term “tissue graft” is used herein to encompass all of these tissue replacement items.
In general, the replacement tissue graft is implanted by securing one end of the tissue graft in a socket formed in a passage formed within the femur (i.e. femoral channel) and passing the other end of the graft through a passage formed in the tibia (i.e. tibial channel). The graft is then secured to the tibia adjacent to the tibial channel. Generally, sutures are used to affix each end of the tissue graft to a fastener (e.g. an interference screw or a post), which is then secured to the bone. Descriptions of these fasteners and methods of forming the passages through the tibia and femur are described in greater detail in the '520 patent.
Another approach for affixing a tissue graft is described in U.S. Pat. No. 5,306,301 (issued Apr. 26, 1994, known herein as “the '301 patent”) and incorporated by reference. The '301 patent discloses using a fixation button to secure a tissue graft at the femoral cortex. The fixation button has an elongated shape and at least one pair of openings through which a suture may be passed and then tied off.
In this approach, the femoral channel has a portion having a first diameter sized to accommodate a bone block and a second portion having a smaller diameter through which the bone block cannot pass. By measuring the total length of the femoral channel and the length of the larger portion, the surgeon determines a “suture span” for attaching the fixation button to the tissue graft.
The surgeon forms an opening in the bone block to be positioned in the femoral channel and threads an end of suture through it. The surgeon then ties the suture to the fixation button, providing the suture span between the button and the bone block. The fixation button and the tissue graft are then passed through the tibial and femoral channels until the graft is properly seated within the socket portion of the femoral passage and the fixation button is firmly seated against the femoral cortex. The tissue graft is then tensioned and anchored at its opposite end using a fixation screw secured within the tibia.
Still another approach for affixing a tissue graft is described in U.S. Pat. No. 5,769,894 (issued Jun. 23, 1998, known herein as “the '894 patent”) and incorporated by reference. The '894 patent describes a graft fixation member configured to allow the length of the suture between the fixation member and the graft to be adjusted and to maintain the adjusted length when the suture is secured to the graft fixation member.
An alternative to tying a suture to a fixation button is disclosed in PCT Application WO 99/47079 (published Sep. 23, 1999, known herein as “the '079 application”) and incorporated by reference. The '079 application discloses an apparatus and method for attaching a continuous loop of suture to a fixation button. Using a series of rollers, the continuous loop is formed from a strand of suture repeatedly coiling the suture through openings in a fixation button. In other examples, a continuous loop of suture may be formed without a fixation member. Continuous loops, both with and without fixation buttons attached, are available from Xiros Limited, Leeds, England, in several sizes. A surgeon selects the closest matching size for a given ACL reconstruction procedure. In other examples, a continuous loop of suture may be formed without a fixation member.